1. Field of the Invention
The present invention relates to an apparatus and a method for signal correction, for correcting an output signal from a signal processing section which processes a measurement signal output from a measurement signal generator (e.g., a sensor).
2. Description of the Related Art
There is often a need to measure a current flowing in a motor for generating driving forces for a vehicle and a battery for that vehicle. A current sensor is usually used as a measurement signal generator for generating a measurement signal based on which such a current is measured. Since various control processes may be performed on the basis of the output from a current sensor, it is imperative that the output from the current sensor be accurately measured.
However, some circuits which implement signal processing sections for applying various processes to output signals from current sensors are susceptible to effects of the environmental condition changes. For example, circuits which perform gain adjustment or impedance conversion for signals are susceptible to effects of temperature changes. Due to temperature changes, the output signal from such a circuit for processing output signals from current sensors may undergo a so-called drifting. The drifting of the output signal from such a circuit for processing output signals from current sensors may prevent the accurate transfer of output signals from the current sensors. In the case where a charge amount is calculated based on multiplication results of signals from current sensors, such drifting may lead to worse current errors.
A signal correction apparatus according to the present invention includes: a measurement signal generator for generating a measurement signal; a reference signal generator for generating a reference signal; a signal processing section for processing the measurement signal and the reference signal; a signal measurement section for measuring at a first time the reference signal having been processed by the signal processing section, measuring at a second time the reference signal having been processed by the signal processing section, and thereafter measuring the measurement signal having been processed by the signal processing section; and a correction section for performing a correction on the measurement signal having been processed by the signal processing section and measured by the signal measurement section, based on a change from the reference signal having been processed by the signal processing section and measured at the first time to the reference signal having been processed by the signal processing section and measured at the second time.
Alternatively, a signal correction apparatus according to the present invention includes: a measurement signal generator for generating a measurement signal; a signal processing section for processing the measurement signal; a control section for switching between a first state in which the measurement signal is input from the measurement signal generator to the signal processing section and a second state in which the measurement signal is not input from the measurement signal generator to the signal processing section; a signal measurement section for measuring at a first time a signal output from the signal processing section in the second state as a reference signal, measuring at a second time a signal output from the signal processing section in the second state as the reference signal, and thereafter measuring the measurement signal having been processed by the signal processing section in the first state; and a correction section for performing a correction on the measurement signal having been processed by the signal processing section and measured by the signal measurement section in the first state, based on a change from the reference signal measured at the first time to the reference signal measured at the second time.
In one embodiment of the invention, the correction for the measurement signal having been processed by the signal processing section and measured by the signal measurement section is performed during the operation of a system including the measurement signal generator.
In another embodiment of the invention, the correction for the measurement signal having been processed by the signal processing section and measured by the signal measurement section is performed immediately after activation of a system including the measurement signal generator, wherein the measurement signal and the reference signal measured by the signal measurement section are learned immediately before a halt of the system, wherein the measurement signal learned immediately before the halt of the system is used as the measurement signal having been processed by the signal processing section and measured by the signal measurement section, wherein the reference signal measured by the signal measurement section immediately after activation of the system is used as the reference signal having been processed by the signal processing section and measured by the signal measurement section at the second time, and wherein the reference signal learned immediately before the halt of the system is used as the reference signal having been processed by the signal processing section and measured by the signal measurement section at the first time.
In another aspect of the invention, there is provided a signal correction method used in a system including a measurement signal generator for generating a measurement signal; a reference signal generator for generating a reference signal; and a signal processing section for processing the measurement signal and the reference signal, the method including the steps of: (a) measuring at a first time the reference signal having been processed by the signal processing section, measuring at a second time the reference signal having been processed by the signal processing section, and thereafter measuring the measurement signal having been processed by the signal processing section; and (b) correcting the measurement signal having been processed by the signal processing section and measured in step (a), based on a change from the reference signal having been processed by the signal processing section and measured at the first time in step (a) to the reference signal having been processed by the signal processing section and measured at the second time in step (a).
Alternatively, there is provided a signal correction method used in a system including a measurement signal generator for generating a measurement signal; and a signal processing section for processing the measurement signal, the method including the steps of: (a) switching between a first state in which the measurement signal is input from the measurement signal generator to the signal processing section and a second state in which the measurement signal is not input from the measurement signal generator to the signal processing section; (b) measuring at a first time a signal output from the signal processing section in the second state as a reference signal, measuring at a second time a signal output from the signal processing section in the second state as the reference signal, and thereafter measuring the measurement signal having been processed by the signal processing section in the first state; and (c) correcting the measurement signal having been processed by the signal processing section and measured in step (b) in the first state, based on a change from the reference signal measured at the first time to the reference signal measured at the second time.
In one embodiment of the invention, the step of correcting the measurement signal having been processed by the signal processing section is performed during the operation of the system.
In another embodiment of the invention, the step of correcting the measurement signal having been processed by the signal processing section is performed immediately after activation of the system, wherein the measurement signal and the reference signal measured are learned immediately before a halt of the system, wherein the measurement signal learned immediately before the halt of the system is used as the measurement signal having been processed by the signal processing section, wherein the reference signal measured by the signal measurement section immediately after activation of the system is used as the reference signal having been processed by the signal processing section and measured at the second time, and wherein the reference signal learned immediately before the halt of the system is used as the reference signal having been processed by the signal processing section and measured at the first time.
According to the present invention, a measurement signal having been processed by a signal processing section and measured by a signal measurement section is corrected based on a change from a reference signal having been processed by the signal processing section and measured at a first time to the reference signal having been processed by the signal processing section and measured at a second time. As a result, it is possible to compensate for any drifting of the output signal from the signal processing section due to environmental condition changes (e.g., temperature changes) around the signal processing section for processing the measurement signal output from a measurement signal generator. Thus, it is possible to accurately transfer the measurement signal output from the measurement signal generator without being influenced by environmental condition changes. This is especially advantageous in a system which is required to detect minute changes in a measurement signal output from a measurement signal generator (e.g., a sensor). Examples of such systems include a system which detects the changes in the output of a current sensor for measuring a current flowing through a motor (for generating a driving force for a vehicle) and a battery.
The correction for the output signal from the signal processing section for processing the measurement signal output from the measurement signal generator may be performed during the operation of a system including that measurement signal generator, or immediately after activation of the system. In the case where the correction is performed immediately after activation of the system, it becomes possible to correct any shift in an apparent zero point of the output of the measurement signal generator that may occur during a halt of the system.
Thus, the invention described herein makes possible the advantage of providing an apparatus and a method for signal correction for correcting an output signal from a signal processing section which processes a measurement signal output from a measurement signal generator (e.g., a sensor), thereby compensating for the drifting of the signal due to environmental condition changes (e.g., temperature changes).
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.